Manually propelled wheelchairs equipped with various forms of brakes or control devices are known in the prior art. The most common device consists of a lever operated brake shoe which engages the tire of the wheelchair propulsion wheel to lock such wheel against movement at required times. This arrangement has at least two serious disadvantages. First, the chair occupant must remove his or her hand from the manual propulsion ring of the wheel in order to operate the control lever or mechanism, with the possibility of losing control of the wheelchair. Secondly, the prior art devices cause excessive tire wear and damage, resulting in premature tire failure and expense.
The invention herein completely overcomes these prior art difficulties through provision of a reliable, simple and positive acting anti-rollback mechanism built integrally into the wheelchair propulsion wheels, thus completely eliminating any external controls which require the chair occupant to release the hand rings on the wheels in order to operate the secondary control mechanism.
Briefly stated, the mechanism according to the invention consists of one-way engaging and one-way freewheeling clutch units on the wheelchair propulsion wheels which follow a stationary annular race adjacent each wheel and fixed to the chair frame. Each clutch has associated with it a rotational locking or stop device whose action assures that undesired backward rolling of the wheelchair cannot occur when the clutches are engaged.
A simple override mechanism enables intentional backward rolling of the wheelchair under positive control of the occupant through use of the wheel mounted hand propulsion rings at any time. A spider fixed to each propulsion wheel has a connection with an override means which releases the locking or stop device when manual force in the reverse direction is exerted on the hand ring by the chair occupant. Releasing of the hand ring reactivates the automatic anti-rollback mechanism. Free forward movement of the chair is enabled at all times. No tire wear is involved with the invention and positive control over the chair by its occupant is assured because the hands need never be removed from the manual propulsion rings.
Other features and advantages of the invention will become apparent during the course of the following description.